The invention relates to liquid fuel atomisers.
Nitrogen oxides (NOx) emitted from boiler and furnace plants, for example, have been accused of causing serious pollution problems. The creation of NOx in liquid fuel burners is affected by a number of factors. For example, the relatively high residence times and temperatures experienced by the fuel and combustion air make significant contributions to NOx production from pressure-atomised burners which produce a relatively large high temperature flame.
It has been proposed (see, for example UK Patent No. 1453853, U.S. Pat. Nos. 4,011,996 and 4,087,050 and an article entitled "Control Technique for Nitric Oxide-Development of New Combustion Methods" by Tsuji S., Tsukada M. and Asai M., IHI Engineering Review, Vol. 6. No. 2, September 1973 published by Ishikawajima-Harima Jukogyo Kabushiki Kaisha) to reduce NOx production in such burners by producing a split flame pattern.
During development by the Applicant of an atomiser to generate a split flame pattern, an atomiser design was produced where the oil film was generated around substantially the whole circumference of the atomiser outlet but did not yield a true split flame pattern and the optimisation of the advantages thereof was not achieved. That atomiser was of a similar type to that shown in UK Patent No. 1453853.
The Applicants found also that, using an atomiser in which the split flame effect is achieved by mounting a plurality of rods on the cap nut around the periphery of the outlet from the orifice plate as is described in the above-mentioned article, some oil tends to flow around the backs of the rods and is sprayed back on to the cap nut. Clearly, such spurious oil flows, particularly on the cap nut, will lead to a build up of carbonised deposits on the atomiser to the detriment of the operation of the atomiser.